A vehicle, such as a train, may use different types of brakes for stopping or slowing the vehicle. For example, a train having a plurality of cars may have a regenerative (or dynamic) braking system on powered units, and may also have an air brake system on some or all of the non-powered and powered units. The air brake system may provide air from one or more generally large reservoirs to generally smaller individual reservoirs associated with a piston for actuating one or more brake shoes against one or more wheels. While the regenerative braking system may be used more often than the air brake system, the air brake system may be intended to be employed during emergency situations or when supplemental braking in addition to the regenerative braking system is needed (for example, on a steep grade). Thus, it is important that the air brake system work properly when called upon.
However, air brake systems may be subject to numerous modes of failure, especially in the conditions encountered by traveling vehicles. For example, couplings used in an air circuit (such as to connect portions of a brake pipe for supplying air to the individual pistons and associated reservoirs) may fail, cylinders may become stuck and not actuate properly, and the like. If enough failures occur throughout the system, then an insufficient amount of air braking capability may be present at an emergency.
U.S. federal regulations thus require periodic checking of the effectiveness of the air brake system of trains. For example, an initial inspection may be required at the beginning of a mission. To perform the initial inspection, the air brake system is actuated, and an operator walks the length of the train to confirm that all brakes are operational, and/or to address any brakes that are not operational. Then, the train is stopped at periodic points (e.g., every 1,000 miles or 1,600 kilometers) along its mission, and an operator again walks the length of the train to confirm that all of the air brakes remain operational, and/or address any non-functioning air brakes. The stopping of the train and inspection of the brakes is a time consuming operation, adding to the time and expense of missions, particularly longer missions that may require multiple stops and brake inspections. As conventional air brakes do not provide feedback regarding their operational status during performance of a mission, the train is stopped and visually inspected by an operator to verify the operational status of the individual brakes.
Certain air brake systems use electronic controls that are able to communicate with a central processor onboard a vehicle. Current U.S. federal regulations allow for waivers of the 1,000 mile inspection rule for trains with electronic monitoring of air brakes through electronic polling of cars equipped with electronic controls for air brakes. For example, if 85% of brakes remain in communication with the central processor, then the 1,000 mile inspection is waived. Such electronic controls, however, have several drawbacks. For example, certain individual brakes may be able to communicate with the central processor but not be functional. Further, electronic control systems may be quite expensive.
A need exists for cost-effective and accurate monitoring of brake systems without requiring visual inspection during a stop.